@SoniaB
I would appreciate if you would add it to your OP for those who blindly rush to flash leaked build without knowing the risk. Also, I would appreciate if you can get in touch with OnePlus team and make them aware of this bug posted below by the dev.
So below is a summary regarding leaked Pie firmware/blobs from XDA Recognized Developer and our official LienageOS maintainer, dianlujitao

A warning on leaked Pie buildsAs you're aware, OnePlus started Pie closed beta days ago, and there're already leaked builds. I made a new Lineage build with blobs from one OOS9.0 leak, installed and updated the firmware. On first boot after fw update, when boot animation was done, unexpectedly, I didn't see my launcher desktop as usual, but an "Decryption unsuccessful" warning telling me that my data was corrupted. Undoubtedly, after rebooting to TWRP it failed to mount /data thus I lost everything on my internal storage.

After several experiments I finally figured out the cause:

If your data is encrypted and bootloader is unlocked, after upgrading to Pie modem firmware, there's 100% chance of your data to become corrupted, and probably no way to restore them. The cause is on firmware side, probably something wrong with key migration, so there's no way for 3rd party developers to fix it. Note that which ROM was in use pre-upgrade doesn't matter at all, i.e., if bootloader was unlocked and you were upgrading from OOS 5.0.8(enforce encryption by default) to OOS 9.0, you'll lose all personal data after reboot from recovery installation. Interestingly, everything works as expected if bootloader was locked.

I couldn't comprehend why do they apply diverse low-level strategies to locked and unlocked bootloader. Arguably this is a bug and should be fixed when they started rolling OTA updates to the public, but it's also possible that this is by design and aims to restrict "unsafe" operations. Regardless, always be careful and backup your data before upgrading the firmware in the near future.

To all those who will download and rush to flash leaked builds, please know that it will most probably wipe all your internal storage and also, there maybe a case where you might not be able to flash back the stable OOS 5.0.8. So flash it on your own risk or simply wait for a stable build.

Not true. People might be able to flash the Closed beta, but you have no idea how to downgrade or if a special build will be required.
Some people have reported that flashing it has caused full wipe of data.
Also, you have no idea what issues there may well be with this beta build. Known issues have not been leaked, there is no public reporting of it and no beta has ever been without bugs. No stable either in fact.
However, if you have flashed this build and are happy with it, then good for you

Click to expand...

Then suggestion that just made an open beta to stop what you to trying to convince others stop installing this closed beta. Cheers!